1. Field of the Invention
The invention relates to a device for obtaining an axle-load signal from the mechanically spring-supported drive axle of a lifting axle structure aggregate, comprising the drive axle and a lifting axle, where the lifting axle can be disconnected by applying pressure to at least one pressure means element employing at least one disengagement pressure.
2. Brief Description of the Background of the Invention Including Prior Art
Conventionally, a lifting axle is lifted from the road surface based on pressure application to a pressure means element with a disengagement pressure or a higher pressure and is thereby disengaged in a lifting axle structure aggregate. In this state, the drive axle operates as a single axle and carries the full axle load. Upon pressure release of the pressure means element, which can occur either by action of the vehicle driver, or automatically, the lifting axle can be lowered toward the road surface and thus can be activated and engaged, and the lifting axle structure aggregate can be used as a double axle while its load capability is increased.
The height level of the disengagement pressure depends, amongst other variables, on the momentary axle load of the lifting axle structure aggregate and on the construction lay-out and dimensions of the pressure means element. When a lower pressure than the disengagement pressure is exerted onto the pressure means element, the lifting axle accepts, depending on the level of the pressure, a part of the momentary axle load. If only an ambient pressure prevails in the pressure means element, i.e. the the pressure is completely released in the pressure means element, then the axle-load part, accepted by the lifting axle, is determined only according to the lever relationships in the lifting axle structure aggregate. In this state, the lifting axle is fully engaged.
The axle load or, respectively, the axle-load part of the drive axle, upon disengaged or upon engaged lifting axle, respectively, can be described by the path of a defined point of the drive axle relative to the vehicle chassis and by the pressure of the pressure means element. In case of a fully engaged lifting axle, i.e. where ambient pressure prevails in the pressure means element, the axle-load part of the drive axle is proportional to the axle load of the complete lifting axle structure aggregate and thus also represents a measure for the axial load of the complete lifting axle structure aggregate. In case of engagement and disengagement of the lifting axle, i.e. during the lowering and raising of the lifting axle, the defined point of the drive axle performs a jump along a path representing its position points, which jump cannot be employed and evaluated for determining the axle load.
A device of the kind initially recited is described in the German Patent Application P 3,840,838.4. A three-dimensional characterizing field is disposed on the surface of the signal body, as described in the German Patent Application P 3,840,838.4. This characterizing field exhibits for each configuration of rotary position and axial position of the signal body a predetermined distance from one point of the vehicle chassis. This distance is captured and observed by the tappet guided axially shiftable at the chassis and the distance is transformed by way of the tappet into the axle-load signal to be obtained. Depending on the path of the defined point of the drive axle relative to the vehicle chassis, based on a spring compression of the drive axle, the signal body is rotated around a rotation axis fixed relative to the vehicle chassis and is axially shifted depending on the pressure of the pressure means element in order to obtain a load-dependent setting of the signal body and thus of the characterizing field.
This conventional structure is expensive based on the required three-dimensional characterizing field on the surface of the signal body.